Vitamin A Slows Progression of Retinitis Pigmentosa in Kids

Now the question is how

Children with retinitis pigmentosa who received vitamin A supplementation were associated with slower rate of cone electroretinogram amplitude compared to children who did not, a small study found.

The estimated mean rate of change smaller in the vitamin A cohort for children with this rare genetic disorder compared to children who did not receive vitamin A (-6.2% per year versus -13.2% per year, P=0.01), reported the late Eliot L. Berson, MD, of Massachusetts Eye and Ear Infirmary in Boston, and colleagues.

Writing in JAMA Ophthalmology, the authors highlighted their own 1993 trial in the Archives of Ophthalmology that found that oral vitamin A slowed the course of retinal degeneration in adults with retinitis pigmentosa. After further study, the National Eye Institute recommended in 2008 that "most adults with retinitis pigmentosa and normal liver function should take vitiman A palmitate."

But they noted that patients younger than age 18 were not included in the study, but some parents asked them if their children could take vitamin A. They were told to eat a regular diet, avoid high-dose vitamin E supplement, monitor serum liver function annually and return for a follow-up assessment and dose adjustment every two years. There were a minority of children who did not pursue treatment after advice from their pediatrician, but still returned for follow-up assessment every 2 years. These two groups of children comprised the cohort in this study -- one group where children consistently took vitamin A, and one where they did not receive vitamin A.

An accompanying editorial by Caroline Klaver, MD, and Alberta Thiadens, MD, both of Erasmus Medical Center in Rotterdam, The Netherlands, noted the work of the original study by Berson, who died earlier this month just short of his 80th birthday. They briefly eulogized him, noting his reports on "nutritional treatment for retinitis pigmentosa were groundbreaking and regarded by most as creative and intelligent solutions to reduce the slope of progression of this devastating disease."

Klaver and Thiadens added that others argued "these reports were merely a proof of concept that needed more in-depth validation before accepting it as profound evidence," but that this new study "adds another building block" to the evidence for vitamin A supplementation being beneficial for patients with retinitis pigmentosa.

And still uncertain is the mechanism by which vitamin A may slow the disease's progression, the editorialists said. They reviewed the substance's interactions with retinal cells, which are multifold, and noted several possible mechanisms -- such as somehow overcoming a genetic defect -- but admitted that the available evidence doesn't allow a firm conclusion.

"As great scientists do, Eliot Berson has managed to raise a mysterious and intriguing issue even after his decease," Klaver and Thiadens concluded.

Study Details

The researchers included 55 children in the vitamin A cohort -- over two-thirds were boys, and almost 90% were white. In 25 members of the control cohort, three-quarters were boys and 100% were white. The mean age of both cohorts was around 9. Children were followed up for about 5 years in the vitamin A cohort and about 4.5 years in the control cohort. However, the authors noted that while over two-thirds of the vitamin A cohort returned for a follow-up examination within the recommended 2 years, only 40% of the control cohort did.

The primary outcome was the mean exponential rates of change of full-field cone electroretinogram amplitude without and with adjusting for potential confounders. But the authors found that even in adjusted analyses, there was still a significantly slower rate of decline among the vitamin A cohort.

They argued that based on these estimates, "falling to half baseline amplitude occurred, on average, in 4.9 years in the control cohort and 9.7 years in the vitamin A cohort, a nearly 2-fold difference."

Examining ocular safety, Berson and colleagues found no significant difference between groups with respect to mean rates of change of visual field or visual acuity, the proportions of children whose visual field diameter fell to 20° or less or whose visual acuity fell to 20/200 or less in at least 1 eye during follow-up.

Limitations to the data included its small sample size and retrospective, observational design, with the authors noting that it is "more limited in its implications than the randomized clinical trial in adults that preceded it."

This study was supported by a center grant from the Foundation Fighting Blindness.

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